1. Field of the Invention
The present invention relates to image recording materials which may be used as planographic printing plate materials, color proofs, photo resists or color filters. More particularly, the present invention relates to negative type image recording materials which can be used as planographic printing plate materials that allow direct plate-making by scanning infrared laser beams based on digital signals from a computer, and the like, and a method of plate making using this negative type image recording material.
2. Description of the Related Art
Recently, as recording light sources of a system for carrying out direct plate making from digital computer data, solid-state lasers and semiconductor lasers emitting infrared rays having wavelengths from 760 nm to 1200 nm have gathered attention since high output and compact lasers of this type are easily available. However, since many of the photosensitive recording materials that are useful in practice are sensitive to wavelengths in the visible range of 760 nm or less, images cannot be recorded with these infrared laser devices. Therefore, there is need formaterials capable of forming images with an infrared laser device.
As for image recording materials that can be used for recording with infrared laser devices, U.S. Pat. No. 4,708,925 discloses recording materials containing an onium salt, a phenol resin, anda spectral sensitizer. However, these image recording materials are of a positive type and not of a negative type as in the present invention and make use of an effect of the onium salt and phenol resin to inhibit dissolution into a developing solution. On the other hand, negative type image recording materials are described, for example, in Japanese Patent Application Laid-Open (JP-A) No. 8-276558. These are recording materials composed of a substance that absorbs light and generates heat, an alkali-soluble resin, and a specific phenol derivative having in the molecule 4 to 8 benzene nuclei. However, though this image recording material can attain high printing durability when sufficient heating is conducted, it provides insufficient sensitivity during laser exposure since reactivity thereof is relatively low. There are various suggestions for increasing the sensitivity of these recording materials; however, means for improving sensitivity generally tended to decrease storage stability of the recording materials. In particular, storage stability in high humidity was problematical. Though it is known that high printing durability can be attained even when a resol resin is used as a cross-linking agent, there was a problem that it was poor in stability over time, like the above-described image recording materials.